Fluorescent electric lamp



Jan. 8, 1946. H. J. M CARTHY FLUORESCENT ELECTRIC LAMP Filed Sept. 13, 1941 H9117 J. I McCarthy INVENTOR.

ATrOENE-Y Patented Jan. 8, 1946 FLUORESCENT ELECTRIC LAMP Henry J; McCarthy,- Danvers, Masa, assignor to Sylvania.Electric Products Inc., a corporation of Massachusetts Application September 13, 1941, Serial No. 410,720 1 Claim. (01. ire-122) This invention relates to electric gaseous dis-. charge devices and more particularly to a discharge device in which the switch for pre-heating the filamentary electrode thereof is enclosed in said device.

An object of this invention is to obtain an electric gaseous discharge device which will be as compact and as self-contained as possible with respect to the auxiliary equipment necessary for the operation thereof.

Another object is to provide discharge device, such as a fluorescent lamp with the filament preheating means located within the lamp.

Other objects, advantages and features will be apparent from the following specification taken in conjunction with the accompanying drawing in which:

The figure shows the discharge device of my invention with a circuit therefor shown schematically.

The sealed glass envelope I has the lead-in wires 2 and 3 sealed in the stem 4. The filamentary electrode 5 is suspended between the top of the lead-in wire 3 and the dummy lead-in wire 5. The bimetallic strip has one end thereof attached to the lead-in wire 2 while the other end with the contact 8 thereon, is located near the dummy lead-in wire 8. The lead-in wire 3 is connected to the battery 9 or some source of electrical energy, through the resistance III, while the lead-in wire 2 is connected thereto through the manual switch Ii with the contact i2 thereon. Thegvoltage of the source 9 should be sufiicient for? striking an arc between the electrodes 5 and, -8,for example, 25 volts would be satisfactory in some cases.

As shown in the figure, the circuit through the manua hswiteh II is closed, thus showing the discharge,.-device and the elements therein in the position they assume during operation. When the discharge device is not in operation the manual switch II is open and the contact 8 on the end of the bimetallic strip 1 is closed with the dummy lead 8.

To start the device, the manual switch H is closed. The filamentary electrode 5 becomes heated by the heat conducted thereto through the lead-in wire 3. The heat from the filamentary electrode plus the heat which passes therethrough to the dummy lead-in wire 6 and thence to the bimetallic strip 1 through the contact 8 will heat the bimetallic strip 1 suiliciently to cause the strip 1 to bend away thereby breaking its contact with the element 8. The filaa mentary electrode 5, the bimetallic strip 1 and the lead-in wires 2 and 3 are so spaced that the bimetal will break contact at the moment the electrode 5 has become sufiiciently heated tocarry the discharge. When this takes place, an arc discharge will be set up between the filamentary electrode 5 and the lead-in wire 2, the filamentary electrode 5 serving as the cathode and the lead-in wire 2 serving as the anode. The discharge will generate sufficient heat to prevent the bimetal from re-establishing contact with the wire 6.

The advantages of an electric discharge device of this structure are many. For example, a twocontact fluorescent lamp may be obtained by coating the walls of the glass envelope I with a layer of luminescent material l3. The ability to obtain a fluorescent lamp with only two contacts, both being on the same end of the lamp, is highly advantageous for it has long been desirable in many types of installation where comparative small bulbs using a minimum of space is essential.

This device is designed primarily to operate on direct current. A filling of an inert gas, for example argon, at very low pressure and a small amount of mercury l4 may be introduced into the lamp. However, better diffusion of the discharge is obtained if the argon pressure is less than 1 mm. and in some cases the lamp may operate with a more uniform glow with no inert gas at all and only a filling of mercury vapor. The filamentary electrode is coated with oneof the well known electron-emissive materials, such as barium, strontium, etc.

What I claim is:

An electric gaseous discharge device comprising: a. sealed glass envelope; a pair of lead-in wires sealed in one end only thereof and extending well into said envelope, with one of said wires forming an anode: a support sealed in said envelope end adjacent the other of said wires and having a contact portion: a filamentary cathode mounted between the outer end of said member.

' HENRY J. McCAR'rHY. 

